I haven't checked a map, but since I camp with my son's BSA Troop down around there a ton, I know that, for all practical purposes, anyone who has business anywhere in southern Indiana, especially if he likes driving at eighty MPH, is going to be on I-65 to go to and from Indianapolis or Plainfield.
BTW Atterbury is pretty big. I'll check a map and figure out what county it's in.